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Date: Tue, 13 Apr 2010 18:41:08 +0800
From: Changli Gao <xiaosuo@...il.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
Changli Gao <xiaosuo@...il.com>
Subject: [PATCH] net: batch skb dequeueing from softnet input_pkt_queue
batch skb dequeueing from softnet input_pkt_queue
batch skb dequeueing from softnet input_pkt_queue to reduce potential lock
contention and irq disabling/enabling.
Signed-off-by: Changli Gao <xiaosuo@...il.com>
----
include/linux/netdevice.h | 1 +
net/core/dev.c | 36 +++++++++++++++++++++++++++---------
2 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d1a21b5..f3f8cca 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1336,6 +1336,7 @@ struct softnet_data {
#endif
struct sk_buff_head input_pkt_queue;
struct napi_struct backlog;
+ atomic_t input_qlen;
};
DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data);
diff --git a/net/core/dev.c b/net/core/dev.c
index a10a216..8816204 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2339,10 +2339,11 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu)
__get_cpu_var(netdev_rx_stat).total++;
rps_lock(queue);
- if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {
- if (queue->input_pkt_queue.qlen) {
+ if (atomic_read(&queue->input_qlen) <= netdev_max_backlog) {
+ if (atomic_read(&queue->input_qlen)) {
enqueue:
__skb_queue_tail(&queue->input_pkt_queue, skb);
+ atomic_inc(&queue->input_qlen);
rps_unlock(queue);
local_irq_restore(flags);
return NET_RX_SUCCESS;
@@ -2801,6 +2802,7 @@ static void flush_backlog(void *arg)
skb_queue_walk_safe(&queue->input_pkt_queue, skb, tmp)
if (skb->dev == dev) {
__skb_unlink(skb, &queue->input_pkt_queue);
+ atomic_dec(&queue->input_qlen);
kfree_skb(skb);
}
rps_unlock(queue);
@@ -3111,25 +3113,38 @@ static int process_backlog(struct napi_struct *napi, int quota)
int work = 0;
struct softnet_data *queue = &__get_cpu_var(softnet_data);
unsigned long start_time = jiffies;
+ struct sk_buff_head skb_queue;
+ __skb_queue_head_init(&skb_queue);
napi->weight = weight_p;
do {
struct sk_buff *skb;
local_irq_disable();
rps_lock(queue);
- skb = __skb_dequeue(&queue->input_pkt_queue);
- if (!skb) {
+ skb_queue_splice_tail_init(&queue->input_pkt_queue, &skb_queue);
+ if (skb_queue_empty(&skb_queue)) {
__napi_complete(napi);
- rps_unlock(queue);
- local_irq_enable();
break;
}
rps_unlock(queue);
local_irq_enable();
- __netif_receive_skb(skb);
- } while (++work < quota && jiffies == start_time);
+ while ((skb = __skb_dequeue(&skb_queue))) {
+ atomic_dec(&queue->input_qlen);
+ __netif_receive_skb(skb);
+ if (++work < quota && jiffies == start_time)
+ continue;
+ local_irq_disable();
+ rps_lock(queue);
+ skb_queue_splice(&skb_queue, &queue->input_pkt_queue);
+ goto out;
+ }
+ } while (1);
+
+out:
+ rps_unlock(queue);
+ local_irq_enable();
return work;
}
@@ -5488,8 +5503,10 @@ static int dev_cpu_callback(struct notifier_block *nfb,
local_irq_enable();
/* Process offline CPU's input_pkt_queue */
- while ((skb = __skb_dequeue(&oldsd->input_pkt_queue)))
+ while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
+ atomic_dec(&oldsd->input_qlen);
netif_rx(skb);
+ }
return NOTIFY_OK;
}
@@ -5709,6 +5726,7 @@ static int __init net_dev_init(void)
queue = &per_cpu(softnet_data, i);
skb_queue_head_init(&queue->input_pkt_queue);
+ atomic_set(&queue->input_qlen, 0);
queue->completion_queue = NULL;
INIT_LIST_HEAD(&queue->poll_list);
--
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